Ran into an issue today trying to create a Villager tunnel with either a 90 degree or 45 degreen corner in it. It's 3 wide, with 2 diagonal and a topper. There's no clean way that I've found to actually make a bend without a gap being in the roof.

http://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=1119564094